WIP: Add ViewCatalog API

sql/catalyst/src/main/java/org/apache/spark/sql/catalog/v2/TableCatalog.java

@@ -89,7 +89,7 @@ default boolean tableExists(Identifier ident) {
    * @param partitions transforms to use for partitioning data in the table
    * @param properties a string map of table properties
    * @return metadata for the new table
-   * @throws TableAlreadyExistsException If a table already exists for the identifier
+   * @throws TableAlreadyExistsException If a table or view already exists for the identifier
    * @throws UnsupportedOperationException If a requested partition transform is not supported
    * @throws NoSuchNamespaceException If the identifier namespace does not exist (optional)
    */

sql/catalyst/src/main/java/org/apache/spark/sql/catalog/v2/View.java

@@ -0,0 +1,33 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.catalog.v2;
+
+public interface View {
+  /**
+   * A name to identify this view. Implementations should provide a meaningful name, like the
+   * database and view name from the catalog.
+   */
+  String name();
+
+  /**
+   * SQL text that defines the view.
+   *
+   * @return the SQL query text that defines this view
+   */
+  String sql();
+}

sql/catalyst/src/main/java/org/apache/spark/sql/catalog/v2/ViewCatalog.java

@@ -0,0 +1,91 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.catalog.v2;
+
+import org.apache.spark.sql.catalyst.analysis.NoSuchNamespaceException;
+import org.apache.spark.sql.catalyst.analysis.NoSuchViewException;
+import org.apache.spark.sql.catalyst.analysis.ViewAlreadyExistsException;
+
+/**
+ * Catalog methods for working with Views.
+ */
+public interface ViewCatalog extends CatalogPlugin {
+  /**
+   * List the views in a namespace from the catalog.
+   * <p>
+   * If the catalog supports tables, this must return identifiers for only views and not tables.
+   *
+   * @param namespace a multi-part namespace
+   * @return an array of Identifiers for views
+   * @throws NoSuchNamespaceException If the namespace does not exist (optional).
+   */
+  Identifier[] listViews(String[] namespace) throws NoSuchNamespaceException;
+
+  /**
+   * Load view metadata by {@link Identifier identifier} from the catalog.
+   * <p>
+   * If the catalog supports tables and contains a table for the identifier and not a view, this
+   * must throw {@link NoSuchViewException}.
+   *
+   * @param ident a view identifier
+   * @return the view's metadata
+   * @throws NoSuchViewException If the view doesn't exist or is a table
+   */
+  View loadView(Identifier ident) throws NoSuchViewException;
+
+  /**
+   * Test whether a view exists using an {@link Identifier identifier} from the catalog.
+   * <p>
+   * If the catalog supports views and contains a view for the identifier and not a table, this
+   * must return false.
+   *
+   * @param ident a view identifier
+   * @return true if the view exists, false otherwise
+   */
+  default boolean viewExists(Identifier ident) {
+    try {
+      return loadView(ident) != null;
+    } catch (NoSuchViewException e) {
+      return false;
+    }
+  }
+
+  /**
+   * Create a view in the catalog.
+   *
+   * @param ident a view identifier
+   * @param sql SQL text that defines the view
+   * @return metadata for the new view
+   * @throws ViewAlreadyExistsException If a view or table already exists for the identifier
+   * @throws NoSuchNamespaceException If the identifier namespace does not exist (optional)
+   */
+  View createView(
+      Identifier ident,
+      String sql) throws ViewAlreadyExistsException, NoSuchNamespaceException;
+
+  /**
+   * Drop a view in the catalog.
+   * <p>
+   * If the catalog supports tables and contains a table for the identifier and not a view, this
+   * must not drop the table and must return false.
+   *
+   * @param ident a view identifier
+   * @return true if a view was deleted, false if no view exists for the identifier
+   */
+  boolean dropView(Identifier ident);
+}

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/AlreadyExistException.scala

@@ -45,6 +45,12 @@ class TableAlreadyExistsException(message: String) extends AnalysisException(mes
   }
 }
 
+class ViewAlreadyExistsException(message: String) extends TableAlreadyExistsException(message) {
+  def this(tableIdent: Identifier) = {
+    this(s"View ${tableIdent.quoted} already exists")
+  }
+}
+
 class TempTableAlreadyExistsException(table: String)
   extends TableAlreadyExistsException(s"Temporary view '$table' already exists")
 

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/NoSuchItemException.scala

@@ -46,6 +46,12 @@ class NoSuchTableException(message: String) extends AnalysisException(message) {
   }
 }
 
+class NoSuchViewException(message: String) extends NoSuchTableException(message) {
+  def this(tableIdent: Identifier) = {
+    this(s"View ${tableIdent.quoted} not found")
+  }
+}
+
 class NoSuchPartitionException(
     db: String,
     table: String,